Motorized ground support devices, or lifts, are used for lifting mobility-impaired passengers to an elevated aircraft hatchway. These lifts are known generally as "Vehicle-Mounted Vertical Lift Devices". Due to the special hazards (particularly wind loading) and strict safety standards associated with aircraft and airport tarmacs, both the U.S. and Canada have introduced safety requirements for such lifts.
The American National Standards Institute, Inc. (ANSI) imposes standard ANSI A92.7-1981, entitled--American National Standard Safety Requirements for Airline Ground Support Vehicle-Mounted Vertical Lift Devices which specify materials of construction, quality, load rating and more particularly, stability requirements. Specifically, the standards call for ground support lifts to withstand lateral wind loading (such as from a jet engine blast) of 90 mph without overturning. In Canada, the Canadian General Standards Board has adopted similar stability requirements pursuant to Society of Automotive Engineer's standard SAE ARP 1247, Para. 3.13.1.9.--substantially identical to the ANSI standard.
Powered lifts for aircraft access have been available for several years. The power sources include conventional electrical and internal combustion engines. While the maneuvering of the lifts may be either powered or manual, the means for elevating the deck itself are consistently powered.
The stability of powered lifts in wind conditions is achieved through a combination of high weight (typically greater than 1000 pounds), and a large ground-engaging frame size. As such powered lifts are generally transportable on resilient wheels, ground-engaging feet are sometimes lowered from the lift's frame to further stabilize the lifts during use.
Examples of motorized lifts which meet these standards include: the "Just Mobility Flight Access System", available from Brownie Tank Mfg. Co., Minneapolis, Minn.; and the "Wollard Passenger Access Lift" or "Hobard PAL", from Wollard Airport Equipment Co., Inc., Eau Claire, Wis.
Users associate certain disadvantages with such lifts including: PA1 maintaining a compact and light structure which is important for facilitating hand-powered manoeuvring of the lift to, from and around the close confines around an aircraft, which is in direct conflict with PA1 providing a light weight, preferably hand-operated device for elevating the deck; and PA1 maintaining a small wind profile which directly conflicts with providing PA1 a lightweight substantially aluminum frame supporting a vertically moveable deck; PA1 a lifting mechanism for raising and lowering the deck which incorporates a self locking winching system which utilizes hand-powered cranking to both lift and lower the deck; and PA1 ground-engaging wheels which only operate when the deck is in its lowermost position.
high capital cost; PA2 high maintenance costs; PA2 low reliability particularly where the lift is used infrequently or in low temperatures; PA2 risk of damage to the aircraft while maneuverability and operating the deck; and PA2 difficulty maneuvering on uneven surfaces, ice and snow. PA2 maintaining a substantial mass for better withstanding side wind loading, and PA2 providing as large base structure as possible for creating as large a moment arm so as to resist an overturning moment, PA2 on and off-loading ramp or ramps which necessarily have a upstanding profile (to minimize the impact on the lift's storage and manoeuvrability) and large, continuous aerodynamic surfaces, (screened or meshed ramp surfaces being psychologically unacceptable for supporting passengers) PA2 surfaces associated with the lift's structural and safety functions, and PA2 the elevating device.
Accordingly, there is a need for a more reliable, more versatile, cheaper lift--more particularly, being light and hand-maneuverable.
Unfortunately, providing a light-weight manoeuvrable lift often times introduces conflicting and challenging design criteria, such as:
Several of the above criteria have been satisfied by a known apparatus described in U.S. Pat. No. 4,926,973, issued to the applicant. This reference describes a hand-operated device for lifting mobility impaired persons which is characterized by:
Unfortunately, this apparatus does not meet the above-stated standards for stability.